There are systems that capture packets transmitted in networks, group packets in certain units, and store the packets. In such systems, data is allowed to be redundant in case that stored data is lost.
For example, as a first classification scheme of grouping packets transmitted with a common session, a scheme of maintaining two groups of packets related to the same session is considered. Apart from this scheme, as a second classification scheme of grouping packets transmitted within a period, a scheme of maintaining two groups of packets related to the same period is considered.
However, even when a group of packets are duplicated in this way, a disadvantage that a load on a process of extracting packets related to a certain period in the first classification scheme is large is not resolved. Similarly, a disadvantage that a load on a process of extracting packets related to a certain session in the second classification scheme is large is not resolved. This is because the classification scheme remains simple.
Japanese Laid-open Patent Publication Nos. 2008-124758, 2003-23464, 2003-91468, 2006-309796, 2015-95785, and 2013-061739 are examples of the related art.